1. Field of the Invention
The present invention relates to a vacuum booster and, more particularly, to a vacuum booster which can be easily combined with a vehicle anti-locking brake system to comprise a traction control system.
2. Description of the Related Art
Conventional vacuum boosters used with vehicle braking systems typically comprise a shell having an interior which is divided by a diaphragm into a continuous pressure chamber and an opposing pressure chamber, and a valve casing, which moves in conjunction with the diaphragm, coupled to a master cylinder. To brake the vehicle, the operator of the vehicle depresses the brake pedal, which is attached to the valve casing, so that the valve casing is moved along its longitudinal axis thereby triggering the action of the master cylinder and brake pads.
Usually, negative pressure created in the intake manifold of the vehicle engine is applied to both the continuous pressure chamber and the opposing pressure chamber so that the valve casing is in a state of equilibrium when the vehicle is not being braked. When the operator of the vehicle depresses the brake pedal, however, the opposing pressure chamber is exposed to the atmosphere thereby producing a pressure differential between both the constant and opposing pressure chambers. This pressure differential is used to assist in braking by supplying an additional force to the valve casing in the same direction as the force due to the operator's depressing of the brake pedal. The conventional vacuum booster is installed in the vehicle so that it operates only when the brake pedal of the vehicle is depressed.
In some cases during the starting or acceleration of a vehicle, the driving wheel performs a slip rotation whereby the steering stability of the vehicle is lost, thus putting the vehicle in danger. In these instances, it is desired to perform a traction control of the driving wheel to prevent the slip rotation thereof. A traction control system can comprise an anti-locking brake system combined with a vacuum booster. However, because the person operating the vehicle does not typically brake the vehicle at the time traction control is needed, a traction control system cannot be built in a simple manner by using an anti-locking brake system and the conventional vacuum booster. To build a traction control system using an anti-locking brake system combined with the conventional vacuum booster, a special hydraulic line, a valve, and so forth would be needed whereby the constitution of the system would be very complicated.